Phosphate ester and quaternary amine compounds are well known and have been widely used for many years for a variety of applications including those requiring surfactant properties. Known phosphate esters do not generally exhibit any antimicrobial characteristics, and while quaternary amine compounds are known in general to exhibit antimicrobial activity, such compounds are extremely irritating and thus have limited usefulness in personal care and cosmetic products. More recently, various betaine-type derivatives having, in general, quaternized alkyl amine groups and at least one phosphorous-containing anion in the molecule referred to hereinafter as "synthetic phospholipids", have been disclosed and suggested as, for example, in U.S. Pat. Nos. 4,215,064; 4,233,192 and 4,380,637 to Lindemann et al., U.S. Pat. Nos. 4,209,449; 4,336,385 and 4,503,002 to Mayhew et al., and U.S. Pat. Nos. 4,243,602; 4,283,542 and 4,336,386 to O'Lenick et al. These synthetic phospholipids are suggested as exhibiting an outstanding combination of surfactant characteristics as well as being well tolerated by human tissue, i.e., they exhibit exceptionally low ocular irritation and oral toxicity. While these known phospholipids have been found useful as surfactants in a variety of personal care, household cleaning and the like products, such products also require the incorporation of antimicrobial preservatives to inhibit microbial spoilage and increase the shelf life.
It is well known that there is a need for effective preservatives in a wide variety of applications where inhibiting the growth of microorganisms is necessary, as for example, personal care products such as shampoos, creams, lotions, cosmetics, liquid soaps, and household products such as fabric cleaners and softeners, hard surface cleaners and the like. The shelf life of these preparations depends on their resistance to microbial spoilage. In addition, antimicrobial agents are a matter of substantial commercial importance in many industrial applications and products such as in paint, wood, textiles, adhesives and sealants, leather, plastics, oil, rubber and metal working fluids etc.
Certain compounds have long been known and used commercially as preservatives. For example, 1,3-dimethylol-5,5-dimethylhydantoin (DMDMH) is useful as a formaldehyde donor for the preservation of personal care products, cosmetics and household products and halopropynyl carbamates are known for their fungicidal activity. Other commercially known preservatives include Quaternium-15 (DOWICIL 200 from Dow Chemical Company); Imidazolidinyl urea (GERMALL 115 from Sutton Laboratories); formaldehyde in the free state, as in formalin; alkyl parabens (e.g. methyl, ethyl and propyl) etc. While such materials have achieved commercial acceptance for many personal care and household products, they generally present a variety of limitations for such use including being unduly expensive; exhibiting limited anti-microbial or antifungal activity, or limited solubility in water; exhibiting undue pH dependence, adverse toxicological properties and skin sensitization or possible carcinogenicity; or they may be inactivated by commonly used materials.
Various synergistic combinations of ingredients have been also suggested for use as preservatives in certain applications such as, for example, disclosed in U.S. Pat. Nos. 3,699,231; 3,929,561; 4,454,146; 4,655,815; but these compositions generally exhibit unfavorable toxicity characteristics, particularly skin and eye irritation, and are not suitable for personal care and household products, and the development of effective, inexpensive, multifunctional products having a broad spectrum activity has long been sought.